The present invention is directed to a highly reactive hydraulic binder for the preparation of building, construction and raw materials.
Conventional hydraulic binders, such as cement and chalk, have setting times of about 5 hours and a characteristically slow time for strength development. However, in many applications, e.g., the repair of streets, bridges, runways etc., quick hardening is very important.
With shorter repair times, the aforementioned constructions may be opened, and thus, enormous costs may be saved. Thus, quick development is of economic interest.
Oil shale is a fossilized energy carrier, containing a considerable amount of organic material in a matrix of fine inorganic minerals. In order to obtain the oil from oil shale, the organic substance, the kerogen, must be thermically decomposed. It remains an inorganic residue, which is denoted as burned oil shale. A large amount of today's burned oil shale must be disposed of, unused, in dumps.
The biggest deposits of oil shale are located in the United States of America, Brazil, USSR, Canada, Italy, Germany and Australia.
In addition to the denotations oil shale, bituminous slate and kerogen rocky material, also some names refer to similar materials of a distinct deposit or of an area, such as slate coal, coorongite, ichthyol slate, kukersite, marahunite, posidonien slate, stink slate, tasmanite or torbanite.
The most frequent minerals in the oil shale deposits are quartz, feldspar, different types of clay and different types of carbonates, e.g., calcium carbonate and magnesium carbonate.
Table 1 below shows the mineralogical composition of American oil shale (green river).
TABLE 1 ______________________________________ Portion in Mineral Chemical Formula mass % ______________________________________ dolomite CaMg(CO.sub.3).sub.2 32-33 calcspar CaCO.sub.3 16-20 quartz SiO.sub.2 10-15 clays (illite) K.sub.2 O.3Al.sub.2 O.sub.3.6SiO.sub.2.2H.sub.2 O 11-19 orthoclase KAlSi.sub.3 O.sub.8 4-6 (adularia) plagioclase NaAlSi.sub.3 O.sub.8.CaAl.sub.2 Si.sub.2 O.sub.8 10-12 (albite) zeolite NaAlSi.sub.2 O.sub.6.H.sub.2 O 1-7 (analcime) pyrite, FeS.sub.2 1-3 marcasite ______________________________________
Oil shale is a laminated sediment rocky mineral, which contains more than 33% of ash as well as organic components. On distillation it yields oil, which may be extracted only in unimportant amounts with conventional solvents for petroleum. For energy gain, the oil shale must be decomposed in a suitable manner. In this regard, various carbonization, combustion and gasification processes are known.
The fluid bed process is a commercial combustion process for oil shale and raw materials containing bitumen and with marly characteristics. The main product is burned oil shale, which is used in the civil engineering product industry. Through liberated heat, the temperature of combustion in the furnace chamber is primarily maintained. Additionally, energy is regained.
Due to an optimal temperature of combustion of 800.degree. C., this process supplies a calcination product having hydraulic characteristics, which provides the following compressive strengths according to DIN 1164 without the addition of chalk:
______________________________________ Compressive strength after 3 days .about.5 MPa 7 days .about.16 MPa 28 days .about.33 MPa. ______________________________________
As a specific example North African burned oil shale shows a compressive strength of only 22 MPa after 28 days.
According to DIN 1164 burned oil shale is a hydraulic hardenable compound. It is formed by burning oil shale at about 800.degree. C. in the fluid bed process. It mainly comprises calcium silicates, calcium aluminates, calcium sulfates and reactive silicon dioxide. With X-Rays the following mineralogical phases are detectable: dicalcium silicate, tricalcium aluminate, monocalcium aluminate, anhydrite, calcium oxide and calcium aluminate ferrite.
In Table 2 below, typical chemical compositions are shown.
TABLE 2 ______________________________________ ORIGIN Colorado/USA Western Israel Compounds Scotland USA Germany Tzefa Efe ______________________________________ CaO 5.3% 21.8% 16-60% 44.5% SiO.sub.2 48.5 32.0 12.25 19.0 Al.sub.2 O.sub.3 25.2 7.2 9-12 8.3 Fe.sub.2 O.sub.3 12.1 2.7 6-7 4.3 MgO 2.2 7.5 1.4-2.0 0.7 Na.sub.2 O + -- 2.3 -- 1.1 K.sub.2 O P.sub.2 O.sub.5 -- -- -- 2.4 SO.sub.3 -- -- 9-10 8.5 Organic -- -- -- 0.9 portion CO.sub.2 -- -- -- 6.2 Loss at -- 20.0 -- 11.3 red heat ______________________________________
Burned oil shale relatively slow hydraulic hardening, which is due to its solidification behavior. According to DIN 1164, setting begins at about 2.5 hours, and ends at about 5 hours.
Burned oil shale is used for the preparation of Portland oil shale cements of different strength classes, whereby the portions of the Portland cement clinker may be from 65 to 90%, and the portions of burned oil shale may be from 10 to 35%.
The clinker minerals, especially dicalcium silicate and calcium aluminate, as well as the reaction of the burned chalk with silicon dioxide, are reasons for the hydraulic hardening of burned oil shale. Simultaneously, a formation of ettringit (calciumsulfoaluminate) takes place. For several applications the characteristics common to burned oil shale and its mixtures with Portland cement, such as slow setting times and low strength development, are not sufficient.